Background package with tikz externalization

Question

I have a follow up question of the thumb index presented in Show current chapter number on each page margin. When I use it alone it works ok. However, when I use it in combination with tikz externalization, the externalization routine starts by generating one empty pdf file per page on the document and ends with the error

Package tikz Error: Sorry, the system call 'pdflatex -shell-escape -halt-on-e.

You can see in the MWE below that I have added \tikzexternalizedisable in several places but it does not seem to work.
Any idea what am I doing wrong?

%%MEW
            % !TeX encoding = UTF-8
            \documentclass[b5paper]{book}
            \usepackage[english]{babel} 
            \usepackage{graphicx}       % Graphics 
            \usepackage{lipsum}

            \usepackage{tikz}
            \usetikzlibrary{external}
            \usepackage{pgfplots}
            \usepgfplotslibrary{external}

            %

            %% THUMB INDEX
            \usepackage{tikzpagenodes}
            \usepackage{totcount}
            \usepackage[contents={},opacity=1,scale=1,color=white]{background}

            \newif\ifMaterial

            \newlength\LabelSize
            \setlength\LabelSize{1cm}

            \AtBeginDocument{%
                \regtotcounter{chapter}%
            }
            \makeatletter
            \tikzexternaldisable
            \newcommand\AddChapterBoxes{%
                \Materialtrue
                \AddEverypageHook{%
                    \tikzexternaldisable        
                    \ifMaterial
                    \ifodd\value{page}%
                    \tikzexternaldisable
                    \backgroundsetup{
                        angle=0,
                        position={current page.east|-current page text area.north east},
                        vshift=-45-(\thechapter-1)*90pt,
                        hshift=0*\LabelSize/2,
                        contents={%
                            \tikz\node[ch label, inner xsep=\LabelSize/2] {\hspace*{-\LabelSize}\thechapter};
                        }%
                    }%
                    \tikzexternalenable
                    \else
                    \tikzexternaldisable
                    \backgroundsetup{
                        angle=0,
                        position={current page.west|-current page text area.north west},
                        vshift=-45-(\thechapter-1)*90pt,
                        hshift=0*\LabelSize/2,
                        contents={%
                            \tikz\node[ch label, inner xsep=\LabelSize/2] {\thechapter\hspace*{-\LabelSize}\null}; % 
                        }%
                    \tikzexternalenable
                    }%
                    \fi
                    \BgMaterial
                    \else\relax\fi
                }%
            }
            \newcommand\RemoveLabels{\Materialfalse}
            \tikzexternalenable
            \makeatother

            \tikzset{
                ch label/.style={fill=black,anchor=west,text width=\LabelSize, align=center,minimum height=\LabelSize,minimum width=\LabelSize*2,inner sep=0em,text=white,font=\sffamily\fontsize{15pt}{0pt}\selectfont}
            }

            %\tikzexternalize[prefix=FiguresTikz/] % uncomment to cause the error


            \begin{document}
                \tikzexternaldisable
                \AddChapterBoxes
                \tikzexternalenable
            \chapter{Test 1}
            \lipsum[1]
            \begin{figure}
                \tikzsetnextfilename{test_figure}
                \centering
                    \begin{tikzpicture}[draw=black,scale=1, trim left]
                    \draw[fill=blue!50] (0,0) rectangle (2, 1) node[midway,font=\tiny,align=center] at (0,0) {test figure};
                    \end{tikzpicture}
                    \caption{test figure}       
            \end{figure}
            %
            %
            \chapter{Test 2}
            \lipsum[2]
            \end{document}

Answer 1

You can set the external/only named key, e.g. by changing \tikzexternalize[prefix=FiguresTikz/] to \tikzexternalize[prefix=FiguresTikz/,only named] to only externalize pictures that have explicitly been named.